This invention relates to a method and apparatus for determining certain operating and running parameters in an internal combustion engine, and more particularly to an improved method and apparatus for determining the time in the combustion cycle at which peak rate of heat release occurs in the combustion chamber and for determining NO.sub.x emissions based on the detected luminosity in the combustion chamber of an engine. This information can be then used for operating and controlling the engine.
With modern technology and electronics, many of the components and running conditions of an internal combustion engine can be controlled more accurately than with previously mechanical systems. For example, the control of the air/fuel ratio, spark timing, fuel injection timing and pulse, and other adjustable factors of engine operation are greatly facilitated through the use of electronic components and computers. However, in order to accurately sense the running of the engine and the phenomena occurring within the combustion chamber, it is necessary to provide a sensor that is directly positioned within the combustion chamber or in proximity to it and which senses the actual combustion process in the engine.
It has been understood that knocking can be determined by an optical sensor that operates within the combustion chamber and which senses the luminosity of the gases in that chamber. A wide variety of knock detectors have been proposed that employ such sensors. However, the inventors have determined that detected luminosity in the combustion chamber, and in particular, various parameters of the luminosity signal or curve generated from this detected luminosity, can be used to predict the time at which the peak rate of heat release occurs in the combustion cycle and to predict NO.sub.x emissions from an internal combustion engine. These predictions were developed using a large bore, lean burn, highly boosted natural gas engine.
It is, therefore, a principal object of this invention to provide an improved apparatus and method for operating an engine, wherein a luminosity detector and particular parameters of its luminosity signal or curve are used to determine when peak rate of heat release occurs in the combustion chamber and to determine NO.sub.x emissions from the engine. These predicted values can be determined during each cycle of operation, or an average value can be determined over a period of cycles.
It is a further object of this invention to provide an improved system and method for operating and controlling an engine, wherein the engine's adjustable parameters such as air/fuel ratio, spark timing, fuel injection, etc., can be varied in response to the parameters of the luminosity signal or in response to certain predicted operating and running parameters of the engine such as the time in the combustion cycle at which peak heat release rate occurs, air/fuel ratio or NO.sub.x emissions so as to provide better running of the engine and/or reduce cycle to cycle variation.
A type of engine sensor has been proposed that senses the actual luminosity of the gases within the combustion chamber. A wide variety of patents illustrating and describing the use of such sensors have issued including the following: 4,358,952; 4,369,748; 4,377,086; 4,393,687; 4,409,815; 4,412,446; 4,413,509; 4,419,212; 4,422,321; 4,422,323; 4,425,788; 4,468,949; 4,444,043; 4,515,132. For the most part, these patents disclose arrangements wherein the sensor is utilized to sense only total luminosity and to equate the luminosity signal to a knocking signal. However, as previously noted, the inventors have determined that this luminosity signal or curve, and in particular various parameters of that signal, can also be employed to determine particular phenomena occurring in the combustion chamber and as an engine control device.